Frothing agents for the flotation of ores and coal



United States Patent FROTHIN G AGENTS FOR THE FLOTATION OF ORES AND COALRobert B. Booth and John M. Dobson, Stamford, Conn., assignors toAmerican Cyanamitl Company, New York, N. Y., a corporation of Maine NoDrawing. Application December 10, 1952, Serial No. 325,226

4 Claims. (Cl. 209166) This invention relates to an improved process forbeneficiating ores, coal and the like and more particularly is concernedwith the use of new frothing agents in the froth flotation of suchminerals.

Frothing agents are compounds having structural formulas that arecharacterized by the presence of two constituents having oppositeproperties. One part of the molecule is polar and the other part isnon-polar, that is, one part repels water, while the other is wateravid.

It is generally recognized that effective frothers should have only onepolar group. For example, Gaudin in his text Flotation reports thatTaggart, Taylor and Ince in Experiments with Flotation Reagents A. I. M.M. E. Tech. Pub. 204 states that all good frothers, with very fewexceptions, contain one polar group and one only, preferably a groupcontaining oxygen in the hydroxy (OH) or other group. Typical compoundsthat have been Widely used as frothing agents are amyl alcohol, hexylalcohol, cresol, terpineol, xyleonol, etc., all of which, it is to benoted, contain only one hydroxy group.

In accordance with the present invention it has now been found thatdihydroxy compounds such as the various polypropylene glycols areremarkably effective frothers. This is particularly surprising in viewof the fact that the art teaches that only the monohydroxy compounds aregood frothers. The polypropylene glycols of the present invention areeffective producers of a strong froth possessing the physical propertiesrequired for supporting the mineral particles.

It is an advantage of the present invention that these new frothersproduce an equivalent or greater quantity of froth with a materiallysmaller quantity of frothing agent as compared to the standard frotherssuch as pine oil, cresylic acids and certain alcohols and hence aremarkedly superior to these standard frothers in specific frothing power.

Moreover, although it has been proposed to use the lower alkylmono-ethers of propylene glycol and polypropylene glycol as frothers,which are also monohydroxy compounds, tests have shown that it requiresat least one third more of these compounds to produce an equivalentconcentrate in the case of many ores and coal, as it does with thepolypropylene glycols of the present invention. Hence, the compounds ofthe present invention are remarkably superior in specific frothing powerto the lower alkyl monoethers of propylene and polypropylene glycol.Likewise, in the case of many ores the new frothers of this inventionhave been found to produce a lower content of acid-insoluble gangue ascompared either to the standard frothers or to the compounds mentionedabove.

The compounds of the present invention are polyglycols and are preparedaccording to methods known to the art such as by reacting propyleneoxide with propylene glycol according to the equation HOCaHsOH+nC3HeO+HOCHz CHCHaOCHz) IZCHCHaOI-I wherein n represents the number of mols ofpropylene oxide used and wherein in the final product n averages 2 to34. The greater the value of n, the longer is the average chain lengthof the polypropylene glycol produced. The polypropylene glycolscontemplated herein thus include such compounds as the di-, tri-,tetra-, penta-, hexaand higher propylene glycols. The pure compounds as2,695,101 Patented Nov. 23, 1954 "ice such are useful in the presentinvention although the reaction mixtures or mixed fractions are usuallymore desirable as they are usually less costly.

The polypropylene glycols useful in the present invention are perhapsbest defined in terms of their molecular Weights. The average molecularweights of these compounds range from about to about 2100. While boththe lower molecular weight and the higher molecular weight polypropyleneglycols are useful in the present invention, it has been found thatoptimum results are secured with the more median molecular weight rangecompounds, that is, those polypropylene glycols having molecular weightsof from about 400 to about 1100 as in this range not only do suchcompounds possess good frothing characteristics but the cost is usuallysomewhat lower than in the case of the higher molecular weightcompounds.

It is also within the scope of the present invention to use thepolypropylene glycols in conjunction with standard frothers.Furthermore, the polypropylene glycol frothers herein described may bestabilized by, extended by, and used in combination with varioushydrocarbon oils such as kerosene, fuel oils, and the like and thisfrequently effects a reduction in the amount of actual frothing agentthat need be used but without sacrificing the excellent frothingproperties possessed by the polypropylene glycols.

It is also to be understood that since the polypropylene glycols of thepresent invention function solely as frothers and are not effective asmineral collectors, a suitable promoter for the minerals must be used inthe froth flotation process. Suitable promoters such as xanthates,dithiophosphates, hydrocarbon oils, naphthenic acids, fatty acids, resinacids and mixtures thereof, the alkali soaps of such acids and theirmixtures, cationic agents such as the long chain amines and aminederivatives may be used.

The invention will be described in greater detail in conjunction withthe following specific examples in which the parts are by weight unlessotherwise specified.

Example 1 A zinc ore containing sphalarite and assaying 2.85% Zn wasground to about minus 65 mesh, conditioned with 0.5 lb./ ton coppersulfate, and 0.10 lb./ton of technical grade sodiumdiethyldithiophosphate. Varying quantities of frothing agents were usedin a series of separate tests on this ore. Mixed amyl alcohols were usedas frothing agents in the first test for comparison with thepolypropylene glycol frothers. The following results were obtained.

The above data clearly show that less of the polypropylene glycolfrothers were required than the amyl alcohol frothers.

Example 2 A second zinc ore containing sphalarite and assaying 7.1% Znwas treated as in Example 1 with 0.6 lb./ton copper sulfate, 0.11lb./ton of technical grade sodium diisopropyldithiophosphate. Threeseparate flotation tests were conducted on this ore using as frothingagents 0.4 lb./ ton mixed amyl alcohols in the first test, 0.2 lb./tonpine oil in the second test, and 0.1 lb./ ton of a polypropylene glycolof molecular weight 400-450 in the third test. Zinc recoveries andconcentrate assays were as follows:

Concentrate, Percent Zn Frother Recov. Assay 0.4 lb./ton Mixed AmylAlcohols 94. 57 34. 53 0.2 lb./ton Pine Oil 04. 58 33.17 0.1 lb./tnPolypropylene Glycol (mol. wt.=400

As in the preceding example, the above results indicate the superiorityin frothing power of the polypropylene glycol frother over that of theconventional fI'OthlIllZ agents.

Example 3 Pennsylvania anthracite coal fines were conditioned with 2.0lb./ton of fuel oil and varying quantities of frother and then floatedin a Fagergren flotation machine. From a flotation feed containing about24.0% ash the following recoveries of low ash coal were obtained FrotherUsed Coal Concentrate Percent Approx. Percent Type Mol. Wt. 19/ mmWeight s Pine Oi] 0. 80. 1 l4. 3 Methyl Amy] Alcohol O. 5 76. 4 14.0 3000.27 85. 5 14. 2 425 0. 08 83. 6 14. 3 550 0.11 84.2 14.2 1, 025 0. 1482. 6 14. 3 2, 025 0. 27 80. 5 13. 9

The above results indicate that the polypropylene glycol frothers wererequired in considerably less quantity than standard frothers such aspine oil and methyl amyl alcohol to give equal or better coalconcentrates.

Example 4 Samples of bituminous coal fines containing 25.5% ash werefloated with 1.0 lb./ton fuel oil and varying quantities ofpolypropylene glycol frothers as given in the following table, whichalso summarizes the recoveries of coal obtained and the ash contents ofthe coal concentrates. In the first test a technical grade heptanol,commonly used as a frother in coal flotation operations, was used forpurposes of comparison.

As in the foregoing examples, lower amounts of the polypropylene glycolswere required and lower ash contents were obtained when these frotherswere used.

Example 5 A polypropylene glycol in the molecular weight range of400-450 was compared with the methyl ether of tripropylene glycol (afrother in the class of the lower alkyl ethers of polypropylene glycolswhich is preferred in practice) in a flotation test on a second sampleof Pennsylvania anthracite coal fines. The flotation testing procedureemployed in Example 1 was used ing results.

with the follow- Coal Concentrate Frother Used Percent Percent WeightAsh b./ton Polypropylene Glycol 0.08 1 82. 0.126 lb./ton Methyl Ether ofTripropylene Glycol.

Example 6 A comparison also was made with the frother of the precedingexample and with pine oil on a Tennessee sulfide zinc ore (3.0% Zn)which was ground to about minus mesh, conditioned with frother and with0.5 lb./ton copper sulfate, and 0.10 lb./ton technical grade sodiumdiisopropyldithiophosphate as promoter. Zinc recoveries and grades ofconcentrate were as follows:

Concentrate, Percent Z11 Frother Used Recov. Assay 1b./ton Pine 01]lb./ton Polypropylene Glycol lb./ton Methyl Ether of TripropyleneGlycol..

Example 7 Comparative flotation tests on the frothing agents used inExample 6 were made on a sulfide copper ore containing some oxide copperand assaying 0.93% Cu. The ore was ground with 3.35 lb./ton lime and0.025 lb./ton sodium secondary butyl Xanthate and frothing agents asindicated in the following table which also summarizes the metallurgicalresults of the rests.

Copper Concentrate, Percent Cu Frother Used Recov. Assay 0.10 lb./tonPine Oil 0.081b./ton Methyl Ether of Tripropylene GlycoL. 0.06 lbJtonPolypropylene Glycol The above data show that lower quantities of thepolypropylene glycol frother were required than pine oil or the methylether of tripropylene glycol to achieve equal or better metallurgicalresults.

Example 8 Samples of a lead ore were floated after grinding andconditioning with 0.035 lb./ ton of sodium isopropyl xanthate andvarying quantities of frothers as indicated in the following table.Cresylic acid was used in the first test for purposes of comparison. Thefollowing metallurgical results were obtained:

Concentrate, Percent Pb Frother Used Rccov. Assay 0.10 1b./ton CresylicAcid 24 0.081b./ton Polypropylene Glycol (mol. wt.425 op.)

Example 9 A sample of Pennsylvania cement rock, about 86.7% minus 325mesh and containing 71.1% CaCOa was treated with 1.0 lb./ ton crudecalcium lignin sulfonate, 0.62 lb./ ton oleic acid and 0.06 lb./ ton ofa polypropylene glycol frother of approximate molecular weight of400-450 and floated for 7 minutes. The flotation concentrate contained90.6% of the total carbonate present in the feed and assayed 82.4%CaCOs.

Example 10 A Michigan iron ore containing mainly hematite and quartz wasground to about minus 65 mesh and deslimed.

The deslimed portions of the ore were conditioned at about 70% solidswith 2.0 lb./ton sulfuric acid, 1.6 lb./ton heavy fuel oil and 3.0 lb./ton of a water soluble etroleum sulfonate of the green acid type,diluted to about 20% solids and floated for 3.5 minutes to recover iron.After 2.5 minutes of flotation, 0.045 lb./ ton of a polypropylene glycolof molecular weight of 400-450 was added as auxiliary frothing agent.The resulting iron concentrate was cleaned twice by refloating toproduce a final concentrate containing 91.9% of the total iron andassaying 62.1% Fe and 8.9% silica.

Example 11 A quartz sand containing 0.095% FezOs was deslimed andconditioned at high solids with 0.4 lb./ton. H2SO4, 0.6 lb./ ton of a1:1 mixture of oil-soluble and water soluble petroleum sulfonates. 0.4lb./ton fuel oil and 0.08 lb./ ton of a polypropylene glycol frother ofmolecular weight of about 425, and floated at 20% solids to remove thecontaminating iron-bearing minerals. The tailing product containing87.4% of the weight of the feed assayed 0.026% FezOs.

The term ore as used throughout the specification and claims is to beunderstood to refer to solid crude ores containing a valuableconstituent and therefore includes such ores as sulfide, oxide andoxidized ores, metallic and nonmetallic ores, glass sands, feldspars,coal, materials containing soluble salts, etc.

We claim:

1. The method of concentrating ores which comprises subjecting anequeous pulp of said ore to froth flotation in the presence of acollector and in the presence as a frother of a polypropylene glycolhaving a molecular weight in the range of 140 to 2100.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,370,366 Sayve Mar. 1, 1921 1,970,578 Schoeller Aug. 21, 19341,995,915 Burdick Mar. 26, 1935 2,467,369 Bishop Apr. 19, 1949 2,611,485Tveter Sept. 23, 1952 FOREIGN PATENTS Number Country Date 674,258 GreatBritain June 18, 1952 OTHER REFERENCES Journal of Physical Chemistry,vol. XXXVI, January 1932, pp. 132137. (Copy in Scientific Library.)

Journal of the American Oil Chemists Society, vol. 29, pp. 240-243.

1. THE METHOD OF CONCENTRATING ORES WHICH COMPRISES SUBJECTING AN EQUEOUS PULP OF SAID ORE TO FROTH FLOTATION IN THE PRESENCE OF A COLLECTOR AND IN THE PRESENCE AS A FROTHER OF A POLYPROPYLENE GLYCOL HAVING A MOLECULAR WEIGHT IN THE RANGE OF 140 TO
 2100. 